The present invention relates to apparatus for driving tunnels, galleries, roadways, adits and similar excavations referred to for convenience hereinafter simply as "tunnels".
It is known to produce a tunnel with the aid of apparatus in the form of a cutter shield with a plurality of elongate drive members or cutters supported on a frame. The drive members are advanced by means of rams and the frame is drawn up from time to time to progressively extend the tunnel. In order to support the tunnel wall behind the shield, various measures have been adopted in the past. For example, fluid concrete is introduced over sheathing behind the shield to create a permanent tunnel lining. It is known to provide the drive members with rear extensions or tails which form a rear shield within which the concrete can be introduced over the sheathing. German patent specification 2522029 describes apparatus with such prolonged drive members. The sheathing can be coupled to the frame of the cutter shield with the aid of hydraulic piston and cylinder units so that it can be drawn up and adjusted. An annular ring provides an end wall for the concrete reception space located between the rear shield and the sheathing. This ring can also be moved, for example, with hydraulic units and can thus compress the concrete introduced into the space. The driving and concreting operations can take place simultaneously and independently, thus saving considerable time. One drawback is, however, as the drive members are advanced, their rear tails leave a gap between the concrete lining and the tunnel wall and subsidence can occur. Other measures can be taken to overcome this problem. German patent specifications 2431652 and 2508407 describe tunnel driving apparatuses in which the drive members of the cutter shield have rear tails which are displaceably supported on an annular component forming a follow-up rear shield located at the rear of the cutter shield frame. The rear shield can be adjusted in relation to the frame. The rear tails of the drive members overlap the rear shield at all times and are thus firmly supported against the tunnel wall.
The frame of the cutter shield of known forms of tunnel driving apparatus usually consists of an open framework on which the drive members are supported and guided. When the tunnel is being driven in waterbearing strata, it is necessary to introduce compressed air into the interior of the cutter shield to maintain excess pressure therein. The compressed air tends to escape from the periphery of the shield, however, and needs to be constantly replaced. To overcome this problem, attempts have been made to provide seals between the drive members but this has not been particularly successful.
A general object of the present invention is to provide an improved tunnel driving apparatus.